The present invention relates generally to resistance welding/brazing operations and in particular, to an improved resistance welding construction that utilizes a non-contact temperature sensor for providing an improved bond between the welded materials and the brazing materials.
The monitoring and control of resistance spot welding devices are well known in the art. Recent prior art constructions have focused on the displacements of the electrodes during welding to achieve an improved welding operation. For example, U.S. Pat. No. 5,789,719 is directed to the fixing of the electrodes against outward displacement when the metal workpieces expand during the application of welding current and permitting inward displacement of the electrodes after the softening of the metal nugget.
However, the prior art resistance welding arrangements are still less than satisfactory. That is, the quality of the resistance weld is sensitive, and therefore dependent on a variety of factors, such as the temperature of the electrodes during use. This temperature may vary, for example, during start-up, where the first few welds may require a longer time to produce a satisfactory weld. Additionally, electrode erosion or electrode wear will produce unsatisfactory results because the current transfer from the electrodes to the material is compromised creating resistance variations. Additionally, variations in the weld can be produced by differences in the material's quality, on the material's finish, or the interface coating on the materials. One or all of these variations can occur at any given moment in a resistance brazing process and the welding operator needs to compensate for the foregoing variables by adjusting the welding control parameters (time, % current, cycles) to achieve satisfactory results. This intensive and accurate human interface in the resistance brazing process can lead to undesirable, and less than satisfactory results.
An attempt at improving the resistance welding operation is described in U.S. Pat. No. 5,672,943. However, this U.S. patent more particularly focuses its improvement methodology on the forces applied to the electrodes during operation to improved the welding process.
It is difficult to evaluate finished products for their quality of braze without sophisticated sonar and/or other techniques, and therefore, it is desirable to provide a system for monitoring and controlling a resistance welding operation that both improves the quality of the products produced thereby while simultaneously reducing the intensive and accurate interfacing needed between the system and the system operator. The present invention disclosed herein achieves the aforementioned and below mentioned objectives.